Known dry-cleaning processes consist of a wash, rinse, and drying/draining cycle with solvent recovery. During this process, items, such as garments, are loaded into a basket positioned within a vessel and immersed in a dry-cleaning solvent pumped into the vessel from a base tank. Conventional dry-cleaning solvents include perchloroethylene (PCE), petroleum-based or Stoddard solvents, CFC-113, and 1,1,1-trichloroethane, all of which are generally aided by a detergent. The use of these solvents, however, poses a number of health and safety risks as well as being environmentally hazardous.
To minimize these problems, dry-cleaning systems that use liquified gas as a cleaning medium, such as liquid carbon dioxide, have been developed. An example of such a cleaning system is found in U.S. Pat. No. 5,339,844 entitled "Low Cost Equipment For Cleaning Using Liquifiable Gas." This system includes a source of liquified gas, an enclosed pressure vessel that forms a cleaning chamber for containing items to be cleaned and a bath of the liquified gas, and a circulatory system for circulating the liquified gas between the source and the vessel. Additionally, as is typical of the prior art, the system utilizes a compressor in the circulatory system, positioned remotely from the pressure vessel, which is used to evacuate gaseous vapors in the vessel released during a cleaning cycle.
Such liquified gas dry-cleaning systems, however, have substantial disadvantages. For example, during the vapor recovery cycle of the dry-cleaning process, heat must be supplied to the vessel to prevent the interior temperature from descending below a prohibitively low level. In currently used systems, this heat is provided by electrical heat exchangers. However, the costs associated with operating these heat exchangers is relatively expensive and, as a result, undesirably diminishes the rate of return dry-cleaning operators can expect to receive. Additionally, the arrangement of using a separate compressor that is typically located 6-8 feet away from the vessel undesirably uses space that could be used, for example, to position another cleaning system. As such, it is seen that a need exists for an improved dry-cleaning system that addresses these problems.